This invention relates generally to piezoelectrically actuated flextensional transducer arrays and method of manufacture, and more particularly to such transducer arrays which can be used as ultrasonic transducers, fluid drop ejectors and in scanning force microscopes.
Fluid drop ejectors have been developed for inkjet printing. Nozzles which allow the formation and control of small ink droplets permit high resolution, resulting in printing sharper characters and improved tonal resolution. Drop-on-demand inkjet printing heads are generally used for high-resolution printers. In general, drop-on-demand technology uses some type of pulse generator to form and eject drops. In one example, a chamber having a nozzle orifice is fitted with a piezoelectric wall which is deformed when a voltage is applied. As a result of the deformation, the fluid is forced out of the nozzle orifice and impinges directly on an associated printing surface. Another type of printer uses bubbles formed by heat pulses to force fluid out of the nozzle orifice.
There is a need for an improved fluid drop ejector for use not only in printing, but also, for photoresist deposition in the semiconductor and flat panel display industries, drug and biological sample delivery, delivery of multiple chemicals for chemical reactions, DNA sequences, and delivery of drugs and biological materials for interaction studies and assaying. There is also need for a fluid ejector that can cover large areas with little or no mechanical scanning.
Various types of ultrasonic transducers have been developed for transmitting and receiving ultrasound waves. These transducers are commonly used for biochemical imaging, non-destructive evaluation of materials, sonar, communication, proximity sensors and the like. Two-dimensional arrays of ultrasound transducers are desirable for imaging applications. Making arrays of transducers by dicing and connecting individual piezoelectric elements is fraught with difficulty and expense, not to mention the large input impedance mismatch problem that such elements present to transmit/receiving electronics.
Scanning force microscopes have been applied to many kinds of samples which cannot be imaged by the other scanning probe microscopes. Indeed, they have the advantage of being applicable to the biological science field where, in order to image living biological samples, the development of scanning force microscopes in liquid with minimum heat production specification is needed. In addition, non-contact scanning force microscopes operating in liquid would permit imaging soft and sensitive probe lithography and high density data storage. Two dimensional arrays of atomic force probes with self-exciting piezoelectric sensing would provide a scanning force microscope which would meet the identified needs.
It is an object of the present invention to provide a flextensional piezoelectric transducer array for use in ultrasonic transducers, droplet ejectors and scanning force microscopes.
It is another object of the invention to provide a fluid drop ejector having an array of piezoelectrically actuated flextensional transducers in which the drop size, drop velocity, ejection rate and number of drops can be easily controlled.
It is another object of the invention to provide a micromachined flextensional membrane array with each membrane having a piezoelectric transducer which is selectively addressed.
It is a further object of the invention to provide a fluid drop ejector in which a membrane including a nozzle is actuated to eject droplets of fluid, at or away from the mechanical resonance of the membrane.
It is another object of the present invention to provide an array of piezoelectric flextensional transducers which can be used for sending and receiving sound, and which can be selectively addressed for ultrasonic imaging.
It is a further object of the present invention to provide an array of flextensional piezoelectrically actuated membranes which are electrostatically positioned.
The foregoing and other objects are achieved by an array of flextensional membranes, each provided with a piezoelectric transducer which can activate the membrane and/or provide a signal representing membrane displacement.